This invention relates to a work machine, such as an excavator, backhoe, front shovel or material handler, more particularly to the structure of a stick and/or boom for use with the work machine.
In a typical arrangement, the boom and stick have an enclosed, box like configuration. For example, U.S. Pat. No. 3,220,578 discloses a stick having an enclosed, box-like shape.
Structural members for work machines such as backhoes, excavators and front shovels typically include a boom pivotally attached to a machine frame at a first end, a stick pivotally attached to the boom at a second end and a bucket or material handling device further attached to the stick. Drive mechanisms, often hydraulic cylinders, are coupled to the machine in manner that moves the boom relative to the machine frame, the stick relative to the boom and the material handler relative to the stick.
In order to achieve the desired movement of structural members, sticks and booms are typically have three pivot (attachment) points. Two of the three pivot points are typically disposed at the first and second end, respectively, of the boom or stick. The first and second pivot points typically define a first longitudinal axis. The third pivot point is typically disposed at a predetermined distance from the first longitudinal axis. A second axis can be defined by extending a line from the first pivot point to the offset pivot point and a third axis can be defined by extending a line from the second pivot point to the offset pivot point. The first longitudinal axis, the second axis and the third axis form a triangle.
A problem with the box-like configuration is that such a structure is high in cost to manufacture and heavy in weight. When the boom or stick is unnecessarily heavy, the amount of material such as dirt or rock that can be carried by a bucket is reduced, thus requiring extra bucket loads to fill a truck. The additional weight also induces additional stress into other components of the work machine; this may adversely effect the life of the work machine. The power requirements to lift or move the additional weight increases the engine and related component size, resulting in increased machine cost. Unnecessary weight, generally, reduces efficiency and increases operating costs of the machine.
The present invention is directed toward overcoming one or more of the problems set forth above.
In an embodiment of the present invention, a work machine having at least one of a boom and a stick. A material-handling device is attached to the boom or stick. The boom or stick being constructed of a box portion and an attached truss portion.
In another embodiment of the present invention, a structural member for a work machine is disclosed. The structural member has a first end and a second end, a first pivot point disposed adjacent the first end and a second pivot point is disposed adjacent the second end. The structural member comprises an offset pivot point having a plurality of longitudinal members extending to the box section, forming a rigid structure.
In yet another embodiment of the present invention, a method of reducing the weight in one of a stick and boom of a work machine. The method includes constructing a box portion having a first pivot point, a second pivot point and a first longitudinal axis extending therethrough. A truss portion is constructed having a plurality of longitudinal members intersecting a third pivot point. Attaching the truss section to the box section completes the stick or boom.